When using an ordinary needle to get a blood sample from or to inject medication in a blood vessel, we enter blindly through the skin and tissue to reach the vessel, so it is possible to get in and continue out of the vessel without even knowing that we pass through it, which unfortunately will rupture the vessel and cause discomfort to the patient, so one application of the spring hypodermic needle is that it prevents the blindly passing through a vessel. Another application is with many emergency cases when we have a collapsed patient who needs immediate cannula insertion, and in those cases the blood vessels are collapsed and attenuated, which makes it difficult to get in, so the usage of the spring hypodermic needle and cannula will make it easier and quicker to get inside a vessel and save patient's life. Another application is in lumber puncture procedure, as it is known we enter blindly using regular needles that may eventually induce injuries and serious complications to the spine, and by using the spring hypodermic needle we will know immediately when the needle just gets inside the spinal cavity, so we avoid and prevent serious complications.